Surgical access for electrical stimulation of the pudendal and dorsal genital nerves in the overactive bladder: a review

High-density spinal cord stimulation selectively activates lower urinary tract nerves

Objective.Epidural spinal cord stimulation (SCS) is a potential intervention to improve limb and autonomic functions, with lumbar stimulation improving locomotion and thoracic stimulation regulating blood pressure. Here, we asked whether sacral SCS could be used to target the lower urinary tract (LUT) and used a high-density epidural electrode array to test whether individual electrodes could selectively recruit LUT nerves.Approach. We placed a high-density epidural SCS array on the dorsal surface of the sacral spinal cord and cauda equina of anesthetized cats and recorded the stimulation-evoked activity from nerve cuffs on the pelvic, pudendal and sciatic nerves.Main results. Here we show that sacral SCS evokes responses in nerves innervating the bladder and urethra and that these nerves can be activated selectively. Sacral SCS always recruited the pelvic and pudendal nerves and selectively recruited both of these nerves in all but one animal. Individual branches of the pudendal nerve were always recruited as well. Electrodes that selectively recruited specific peripheral nerves were spatially clustered on the arrays, suggesting anatomically organized sensory pathways.Significance.This selective recruitment demonstrates a mechanism to directly modulate bladder and urethral function through known reflex pathways, which could be used to restore bladder and urethral function after injury or disease.

A Computational Study of Lower Urinary Tract Nerve Recruitment with Epidural Stimulation of the Lumbosacral Spinal Cord

Bladder dysfunction is a major health risk for people with spinal cord injury. Recently, we have demonstrated that epidural sacral spinal cord stimulation (SCS) can be used to activate lower urinary tract nerves and provide both major components of bladder control: voiding and continence. To effectively control these functions, it is necessary to selectively recruit the afferents of the pudendal nerve that evoke these distinct bladder reflexes. Translation of this innovation to clinical practice requires an understanding of optimal electrode placements and stimulation parameters to guide surgical practice and therapy design. Computational modeling is an important tool to address many of these experimentally intractable stimulation optimization questions. Here, we built a realistic MRI-based finite element computational model of the feline sacral spinal cord which included realistic axon trajectories in the dorsal and ventral roots. We coupled the model with biophysical simulations of membrane dynamics of afferent and efferent axons that project to the lower urinary tract through the pelvic and pudendal nerves. We simulated the electromagnetic fields arising from stimulation through SCS electrodes and calculated the expected recruitment of pelvic and pudendal fibers. We found that SCS can selectively recruit pudendal afferents, in agreement with our experimental data in cats. Our results suggest that SCS is a promising technology to improve bladder function after spinal cord injury, and computational modeling unlocks the potential for highly optimized, selective stimulation. Clinical Relevance - This model provides a method to non-invasively establish electrode placement and stimulation parameters for improving bladder function with epidural spinal cord stimulation.

Neurostimulation in neurogenic patients

PURPOSE OF REVIEW

To provide an overview of available electrical stimulation devices in neurogenic patients with lower urinary tract disease.

RECENT FINDINGS

It is advocated to do more studies in neurogenic patients as results seem promising and useful but most studies did not include neurogenic patients or neurogenic patients were not analyzed or reported separately. Most studies included a small heterogenous neurogenic group with multiple pathophysiologic origin focusing on effect of a treatment instead of results of a treatment in a specific neurogenic group. Neuromodulation or stimulation has the advantage that it acts on different organs, like bladder and bowel, so can treat neurogenic patients, who mostly suffer from multiple organ failure.

SUMMARY

Brindley procedure, sacral neuromodulation (SNM) and posterior tibial nerve stimulation (PTNS) are available for a while already. The Brindley procedure (including sacral anterior root stimulation in combination with a rhizotomy of posterior sacral roots) is developed for selected spinal cord injury patient with a complete spinal injury, and has shown results for many years in neurogenic patients. An alternative to the rhizotomy is not established yet. SNM and PTNS are other modalities that are used in nonneurogenic patients, but are not yet indicated and much studied in neurogenic patients.

Electrical stimulation of the pudendal nerve promotes neuroregeneration and functional recovery from stress urinary incontinence in a rat model

The pudendal nerve can be injured during vaginal delivery of children, and slowed pudendal nerve regeneration has been correlated with development of stress urinary incontinence (SUI). Simultaneous injury to the pudendal nerve and its target muscle, the external urethral sphincter (EUS), during delivery likely leads to slowed neuroregeneration. The goal of this study was to determine if repeat electrical stimulation of the pudendal nerve improves SUI recovery and promotes neuroregeneration in a dual muscle and nerve injury rat model of SUI. Rats received electrical stimulation or sham stimulation of the pudendal nerve twice weekly for up to 2 wk after injury. A separate cohort of rats received sham injury and sham stimulation. Expression of brain-derived neurotrophic factor (BDNF) and β_II-tubulin expression in Onuf's nucleus were measured 2, 7, and 14 days after injury. Urodynamics, leak point pressure (LPP), and EUS electromyography (EMG) were recorded 14 days after injury. Electrical stimulation significantly increased expression of BDNF at all time points and β_II-tubulin 1 and 2 wk after injury. Two weeks after injury, LPP and EUS EMG during voiding and LPP testing were significantly decreased compared with sham-injured animals. Electrical stimulation significantly increased EUS activity during voiding, although LPP did not fully recover. Repeat pudendal nerve stimulation promotes neuromuscular continence mechanism recovery possibly via a neuroregenerative response through BDNF upregulation in the pudendal motoneurons in this model of SUI. Electrical stimulation of the pudendal nerve may therefore improve recovery after childbirth and ameliorate symptoms of SUI by promoting neuroregeneration after injury.

Clinical utility of neurostimulation devices in the treatment of overactive bladder: current perspectives

Objectives

This review describes the evidence from established and experimental therapies that use electrical nerve stimulation to treat lower urinary tract dysfunction.

Methods

Clinical studies on established treatments such as percutaneous posterior tibial nerve stimulation (P-PTNS), transcutaneous electrical nerve stimulation (TENS), sacral nerve stimulation (SNS) and sacral anterior root stimulation (SARS) are evaluated. In addition, clinical evidence from experimental therapies such as dorsal genital nerve (DGN) stimulation, pudendal nerve stimulation, magnetic nerve stimulation and ankle implants for tibial nerve stimulation are evaluated.

Results

SNS and P-PTNS have been investigated with high-quality studies that have shown proven efficacy for the treatment for overactive bladder (OAB). SARS has proven evidence-based efficacy in spinal cord patients and increases the quality of life. TENS seems inferior to other OAB treatments such as SNS and P-PTNS but is noninvasive and applicable for ambulant therapy. Results from studies on experimental therapies such as pudendal nerve stimulation seem promising but need larger study cohorts to prove efficacy.

Conclusion

Neurostimulation therapies have proven efficacy for bladder dysfunction in patients who are refractory to other therapies.

Significance

Refinement of neurostimulation therapies is possible. The aim should be to make the treatments less invasive, more durable and more effective for the treatment of lower urinary tract dysfunction.

New laparoscopic approach to the pudendal nerve for neuromodulation based on an anatomic study

AIMS

The aim was to develop a new laparoscopic technique for placement of a pudendal lead.

METHODS

Development of a direct, feasible and reliable minimal-invasive laparoscopic approach to the pudendal nerve (PN). Thirty-one embalmed human specimens were dissected for the relevant anatomic structures of the pelvis. Step-by-step documentation and analysis of the laparoscopic approach in order to locate the PN directly in its course around the medial part of the sacrospinous ligament and test this approach for feasibility. Landmarks for intraoperative navigation towards the PN as well as the possible position of an lead were selected and demonstrated.

RESULTS

The visible medial umbilical fold, the intrapelvine part of the internal pudendal artery, the coccygeus muscle and the sacrospinous ligament are the main landmarks. The PN traverses the medial part of the sacrospinous ligament dorsally, medially to the internal pudendal artery. The medial part of the sacrospinous ligament has to be exposed in order to display the nerve. An lead can be placed ventrally on the nerve or around it, depending on the lead type or shape.

CONCLUSIONS

A precise and reliable identification of the PN by means of laparoscopy is feasible with an easy four-step approach: (1) identification of the medial umbilical fold; (2) identification of the internal iliac artery; (3) identification of the internal pudendal artery and incision of the coccygeus muscle ('white line', arcuated line); and (4) exposition of the medial part of the sacrospinous ligament to display the PN.

Subject-Controlled, On-demand, Dorsal Genital Nerve Stimulation to Treat Urgency Urinary Incontinence; a Pilot

OBJECTIVES

To evaluate the effect of subject-controlled, on-demand, dorsal genital nerve (DGN) stimulation on non-neurogenic urgency urinary incontinence (UUI) in a domestic setting.

MATERIALS AND METHODS

Non-neurogenic patients >18 years with overactive bladder symptoms and UUI were included. Exclusion criteria were mainly stress urinary incontinence. Patients underwent 1 week of subject-controlled, on-demand, DGN stimulation, delivered by a percutaneously placed electrode near the DGN connected to an external stimulator (pulse-rate 20 Hz, pulse-width 300 μs). Patients activated the stimulator when feeling the urge to void and stimulated for 30 s. The amplitude was set at the highest tolerable level. A bladder diary including a severity score of the UUI episodes/void (scores: 0 = none, 1 = drops, 2 = dashes, 3 = soaks) and a padtest was kept 3 days prior to, during, and 3 days after the test period. The subjective improvement was also scored.

RESULTS

Seven patients (4 males/3 females) were enrolled, the mean age was 55 years (range 23-73). Six completed the test week. In the remaining patient the electrode migrated and was removed. 5/6 finalized the complete bladder diary, 1/6 recorded only the heavy incontinence episodes (score = 3). 4/6 completed the padtest. In all patients who finalized the bladder diary the number of UUI episodes decreased, in 3/5 with ≥60%. The heavy incontinence episodes (score = 3) were resolved in 2/6 patients, and improved ≥80% in the other 4. The severity score of the UUI episodes/void was improved with ≥ 60% in 3/5 patients. The mean subjective improvement was 73%.

CONCLUSION

This feasibility study indicates that subject-controlled, on-demand DGN stimulation using a percutaneously placed electrode is possible over a longer time period, in a home setting, with a positive effect on non-neurogenic overactive bladder symptoms with UUI. Although the placement is an easy procedure, it is difficult to fixate the electrode to keep it in the correct position. Improvements in hardware, like a better fixated electrode and an easy to control stimulator, are necessary to make SODGNS a treatment possibility in the future.

Laparoscopic placement of a tined lead electrode on the pudendal nerve with urodynamic monitoring of bladder function during electrical stimulation: an acute experimental study in healthy female pigs

Purpose

The aim of this study was to develop a method for standard laparoscopic access to the pudendal nerve in pigs to implant an electrode for chronic neuromodulation studies.

Methods

Using routine laparoscopic surgical techniques, the pudendal nerve was located in 10 female pigs using standardized anatomical landmarks. A tined lead electrode was placed in parallel to the exposed pudendal nerve, and acute unilateral electrical stimulation was performed consecutively on both pudendal nerves. Bladder pressure and perineal skeletal muscle response was monitored during stimulation.

Results

Standard access to the pudendal nerve was successfully established in the pig model with surgical times of approximately 45 minutes for bilateral electrode placement. Acute unilateral stimulation did not evoke bladder responses but resulted in reliable stimulation-dependent activity of the perineal skeletal muscles. The structural integrity of the pudendal nerves was confirmed in all cases.

Conclusions

These results illustrate the effectiveness of laparoscopy for standardised, safe nerve localisation and electrode implantation at the pudendal nerve in pigs. Laparoscopic implantation represents an alternative approach for performing electrode implantation under optical guidance versus the standard approach of percutaneous, neuro-physiological monitored implantation. In the future, pudendal neuromodulation may be used as a supplement to sacral neuromodulation or as a standalone therapeutic approach, depending on the underlying bladder dysfunction.

Transcutaneous electrical nerve stimulation (TENS) improves the diabetic cytopathy (DCP) via up-regulation of CGRP and cAMP

The objective of this study was to investigate the effects and mechanism of Transcutaneous Electrical Nerve Stimulation (TENS) on the diabetic cytopathy (DCP) in the diabetic bladder. A total of 45 rats were randomly divided into diabetes mellitus (DM)/TENS group (n = 15), DM group (n = 15) and control group (n = 15). The rats in the DM/TENS and TENS groups were electronically stimulated (stimulating parameters: intensity-31 V, frequency-31 Hz, and duration of stimulation of 15 min) for three weeks. Bladder histology, urodynamics and contractile responses to field stimulation and carbachol were determined. The expression of calcitonin gene-related peptide (CGRP) was analyzed by RT-PCR and Western blotting. The results showed that contractile responses of the DM rats were ameliorated after 3 weeks of TENS. Furthermore, TENS significantly increased bladder wet weight, volume threshold for micturition and reduced PVR, V% and cAMP content of the bladder. The mRNA and protein levels of CGRP in dorsal root ganglion (DRG) in the DM/TENS group were higher than those in the DM group. TENS also significantly up-regulated the cAMP content in the bladder body and base compared with diabetic rats. We conclude that TENS can significantly improve the urine contractility and ameliorate the feeling of bladder fullness in DM rats possibly via up-regulation of cAMP and CGRP in DRG.

Dorsal genital nerve stimulation in patients with detrusor overactivity: a systematic review

This study evaluates the outcome of trials to stimulate the dorsal genital nerve (DGN) in patients with lower urinary tract dysfunction. The aim of most studies was to suppress detrusor overactivity in patients with overactive bladder (OAB) syndrome by DGN stimulation. A literature search was performed using Pub Med, Web of Science, and Scopus databases (1980 to April 2012) for clinical trials of DGN stimulation in patients with detrusor overactivity. Seventeen studies were found in the literature. In the studies, different patterns of DGN stimulation were applied. The patterns were either continuous, conditional, or semi-conditional; on an acute or on a chronic basis. DGN stimulation lead to improvement of bladder capacity and reduction in urgency and/or incontinence episodes in many patients. The outcomes of conditional stimulation were comparable to continuous stimulation with respect to improvement of bladder capacity. The publications give evidence that DGN stimulation increases bladder capacity and suppresses involuntary detrusor contractions. Implantable DGN stimulation electrodes can open the way for more prolonged studies in larger patient groups to assess the effectiveness of chronic DGN stimulation in patients with OAB syndrome. Chronic DGN stimulation seems to be of value in the management of OAB syndrome.